


Just Once

by corruptfiction



Category: Voltron: Legendary Defender
Genre: Adult/Minor, Anal Sex, Blowjobs, Keith and Shiro are Siblings, Keith is under 18, M/M, Shiro is a legal adult, Sibling Incest, Statutory Rape, keith deserves better
Language: English
Status: In-Progress
Published: 2017-12-29
Updated: 2018-06-26
Packaged: 2019-02-23 11:22:15
Rating: Not Rated
Warnings: Rape/Non-Con, Underage
Chapters: 5
Words: 3,558
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/13189020
Author URL: https://archiveofourown.org/users/corruptfiction/pseuds/corruptfiction
Summary: When Shiro comes home over winter break from college, he doesn't miss the way Keith has started to fill out into his body, and the way his longer hair frames his delicate face..He just wants to kiss him once.Just once.And Keith just wants to make his big brother happy, he hasn't seen him in months, he misses him..





	1. Chapter 1

**Author's Note:**

> Sorry about how hella short this first chapter is. There's going to be more when I edit probably, but I wanted to get some content up while it's still in my head.

"Takashi!"

Shiro turned around, luggage in tow, to see his little brother barrelling toward him. Keith tackled him in a hug and the both fell to the airport floor, laughing. The surrounding passersby hardly spared them a glance, airports were always full of the strangest things, the weirdest people. Eventually, you get used to it.

Keith clambered up off of his brother, muttering a soft, "Sorry," and bending down to get Shiro's luggage for him. He didn't see the way Shiro's eyes wandered to his bottom as he bent, and evidently neither did their parents who made their way over to greet their son.

"You've gotten taller!" Shiro's bright smile aimed at Keith made the younger boy beam.

"I grew an inch!"

The rest of the way home was filled with chatter from all of them as they asked what each other had been up to in the months since Shiro had gone off to college. Keith was eager to tell Shiro every story he had, everything he had been learning in his sixth grade class. Shiro asking if Keith had a girlfriend yet cut the conversation short. Keith turned red and stayed silent until they were back inside of the house they had both grown up in, and Keith was telling him about his high score in Guitar Hero.

. . .

Two days later, their parents were each at work and Shiro was left in charge. He made grilled cheese sandwiches for lunch, cut diagonally just how Keith liked, with tomato soup in a little bowl to the side. Keith was already at the table, going on about what some kid, Lance, said in one of his classes and talking about how 'Lance is so dumb'.

Shiro chuckled and slid a plate and bowl over the Keith. "Eat your lunch, little dude."

"I ain't little, I grew, remember?" Nonetheless, Keith dug into the food, messy as ever. Still no manners, Shiro would have to teach him eventually. But then the soup was all over Keith's lips and Shiro was leaning in.

"You've got some food right there.."

"Where?"

"I'll get it.."

Shiro leaned in and brushed his lips against Keith's, tongue flickering out to lick away the tomato soup. Keith flinched away but at the hurt look on his brother's face he leaned back in.

Shiro slowly moved his lips against Keith's and eventually pulled away and wiped saliva from the corner of his mouth. "Sorry, I, uh.."

"It's okay.. I thought you're only supposed to do that when you're dating someone, or married like mom and dad..? And.. Are two boys allowed to do that?" Keith was surprised, but less disgusted than Shiro expected.

"Well, it's for when you really love someone, so two boys can do it.. I.. I shouldn't have done that, we're brothers, I.. Don't tell anyone about that, okay?"

"Okay..."


	2. Chapter 2

**Summary for the Chapter:**

> Again, sorry it's pretty short. I realized I never added more to the story and wanted to get something out there.

Keith was a good baby brother, he was. He just really loved his older brother, so he wanted to be around him all of the time. Apparently that made him "annoying".

It had been two days, and Keith hadn't mentioned the kiss to anyone.

  
Shiro was thankful for that, he felt very close to his brother, but almost a little too close. Without their parents in the house, and Keith's winter break in full swing, he would just come into Shiro's room and sit. And talk. A few times Shiro had to frantically close web browsers, but after Keith unexpectedly entered three times in the first few hours of their parents being gone it became expected more.

  
Now Shiro played video games. Every few minutes, Keith was scooting just a little closer go his brother, until he was nearly in his lap. He wanted Shiro to pay attention to him, he missed him in that first school year with Shiro off at college.

  
"Shiroooo.." He whined.

  
"Keith, you know I'm in the middle of a battle, what do you want?" Shiro's eyes stayed focused on the TV. Keith grinned.

  
"Kiss me."

  
Shiro's eyes widened and his hands stopped pressing buttons on the controller, his character being overwhelmed and killed almost immediately. Keith laughed softly and climbed into his lap. "Kiss me. Like you did the other day." Shiro sat in shock, controller falling out of his hands as they came up to rest on Keith's hips. Keith didn't wait for Shiro to initiate it; he pressed his lips to his older brother's and did his best to mimic the way Shiro had moved his lips the last time.

  
Snapping out of it, something feral seemed to awaken in Shiro. He held tightly to the younger, pressing his tongue into the preteen mouth and moaning when he felt the other tongue wrap around his own. He carefully flipped them over, pressing Keith down into the bed and crashing their lips together again desperately.

  
This took Keith by surprise, he didn't have a lot of experience but he could feel Shiro's crotch against his leg and knew enough to know that the hardness meant Shiro was.. what was the word his friends used? Horny. he instinctively wrapped his legs around Shiro's waist, enjoying the sensation of his brother rutting against him and kissing him. Shiro was soon pulling off Keith's jacket and shirt, warm hands trailing over his scrawny body and teasing at nipples that had never experienced such a thing before. He trailed his kisses down Keith's neck and down to one, lapping at it tentatively to see Keith's reaction. Keith was arching his back and keening when Shiro suckled the nipple into his mouth and nipped at it gently.

  
The sound of a door opening downstairs brought them both back from the edge.

  
Shiro quickly started redressing his younger brother, with a harsh, "Don't tell." All Keith did was nod.


	3. Chapter 3

**Summary for the Chapter:**

> Actual smut kind of? I still want to try to get some longer chapters eventually but I also want to be updating more often, and I'm not great at doing either of those.

    Keith was a good listener when he wanted to be, so when their dad came into the house he didn't say a thing about what he and Shiro had just been up to. He looked at the clock and realized of course their dad was home now, he always came home around five. Next time, they'd have to take time into account. And Keith knew there would be a next time. He already had the gears in his head spinning, coming up with a plan.  
  
    The next morning, right after both of his parents had left for work, Shiro was still asleep in bed. Keith crawled beneath the covers and curled up against Shiro's warm chest. A groggy, "What are you doing in here," was muttered, but the nineteen year old's arm still came to wrap around his younger brother.  
  
    "Mom and Dad are gone.. so I thought maybe you'd wanna do what we were doing yesterday? it felt nice..."  
  
    In seconds, Shiro's hand was scrunching up Keith's shirt. Calloused fingers twisted the little pink nubs on Keith's chest, making him mewl out at the sensations. "F-feels good," he gasped, Shiro smirking and continuing the movements. He started tugging down Keith's pajama bottoms and briefs and tossed them to the floor. Keith made weak efforts to cover up his cock, not surrounded by hair yet, not quite having hit puberty yet.  
  
    "None of that." Shiro pried Keith's hands away easily and began stroking his cock slowly, as it started to harden for the first time. He kicked off his own pajama bottoms, nothing underneath, already shirtless from choosing to sleep without a shirt on. His erection rubbed against Keith's crack and leaked precome against his back. With the hand not pumping his brother's own hard-on, his fingers trailed over Keith's taint and circled his hole, not pressing in, no lubrication applied yet.  "In the nightstand drawer there's a little bottle, can you get it for me?"  
  
    Keith moaned from the feelings but nodded, leaning over to get the bottle for Shiro and handing it to him quickly. "What's it for?"  
  
    "It's to stretch you open, so we can... make love.. okay?" Shiro squirted some of the cold, clear liquid onto his fingers and soon was pressing one into Keith's virgin hole. "Just push out, like when you go poop, or it'll hurt."  His finger went in to the second knuckle as Keith did as he was told, and soon a second finger was added, following the natural curve of the channel.  
  
    Trying to relax his body, Keith closed his eyes and took deep breaths. This part didn't feel as good, he wished Shiro would go back to playing with his nipples and cock. At least, he thought that until something was struck inside of him and his body instinctively arched. "Shiro!"  
  
    Shiro scissored the two fingers a bit before adding a third, aiming for that spot again as Keith whimpered and begged for him to keep going. When he hit it again, Keith convulsed, his first orgasm taking over him. After a few moments he lay, breathing heavily.  
      
    When the orgasm was over Shiro was quick to start fingering him again, his cock springing back to life soon. Keith whined at the loss when the fingers left, but they were soon replaced by a thick cock, that hit his prostate as soon as pushed in. He dug his fingers into the sheets on his older brother's bed as Shiro thrust into him. Each thrust rocked him forward, ripples of pleasure going through him every time his prostate was hit. He clenched around the invading cock, causing Shiro to bite his neck gently to cover up his moans.  
  
    Keith started moving back against him, desperate for more of the good feelings, the pleasure. His hand moved down to his own cock to stroke himself as he was fucked into the bed. It didn't take long for him to come again with the consistent onslaught on the spot inside of him that the head of Shiro's cock kept hitting. With one hand he clung to Shiro as his orgasm ripped through him.  
  
    Shiro thrust a few more times before it was too much and he spilled his seed into his little brother, muffling his moans against Keith's shoulder. When he pulled out, come seeped out of Keith's used hole onto the bed. He decided to deal with it later, for now he just wanted to go back to sleep.  
  
    "I love you, Shiro.." murmured Keith.  
  
    "I love you too."


	4. Chapter 4

**Summary for the Chapter:**

> Shiro and Keith spend the rest of their day together. Shiro takes care of him.

Keith woke up naked, in someone else's bed. He started to panic for a moment before realizing that the warm chest against his back was Shiro's. Relaxing into the hold, he turned over to look up at Shiro's resting face. He didn't foresee the outcome of kissing his brother to be so.. intimate. So intense. The feeling of his brother's cock inside of him was still fresh in his mind, especially as he sat up and felt the soreness in his bottom. He winced but slowly stood.

“Going so soon..?" Shiro's voice interrupted the silence of the room. Keith turned and smiled at him.

“Mom told me to clean my room before she gets home.. You can come with if you want."

Shiro sat up, exhausted, and grinned. "I have a feeling if I go with you, your room will never get clean. We'd be a bit preoccupied." He spanked Keith lightly; not enough to actually be painful, just a playful swat. Keith's face turned a rosy pink as he started pulling on his clothes.

Keith leaned to press his lips to Shiro's before rushing off toward his room. With a soft laugh as his little brother ran off, Shiro got out of bed to get dressed as well.

Trash was picked up off of Keith's floor, sheets and blankets smoothed out over Keith's bed. He made sure the room was completely straightened out, knowing that even so his mom would no doubt find the one speck of dust he missed. He folded all of his clothes and arranged them in his dresser.

In the kitchen, Shiro cooked eggs and hashbrowns, splitting them up onto two plates. With a ding two pieces of toast popped up from the toaster. Shiro spread jam on both and put one on his plate, one on Keith’s, cut diagonally into two triangular pieces. He set both plates on the dining room table before calling, “Keith, come eat!”

The twelve year old was quick to come out and take his seat, thankful for the food Shiro made. “You didn’t have to make breakfast, we could’ve just had cereal.. And it’s like noon.” Keith let out a quiet giggle and smiled at his older brother. Shiro just ruffled his hair.

“Then I guess I can have yours, since you just want cereal?”

“No! I want it!”

Shiro let out a warm chuckle as he sat down and they both dug into their food.

Both of the boys took their dishes into the kitchen afterward, and Shiro put the plug in as he squirted a few drops of dish soap in and filled the sink with soapy water. Keith started to head back to his room, until Shiro cleared his throat in such a forced way that Keith knew he had to come help clean.

“You wash them, I’ll dry them, and we can have this done in five minutes.”

Keith could agree with that. He dunked his hands into the water and grabbed the sponge before scrubbing at a dirty plate. He rinsed it and passed it to Shiro, who wiped it down with a clean washcloth before putting it in the cupboard. They continued with the rest of the dishes and it was all done relatively quickly. Keith removed his hands from the soapy water, now covered in bubbles. A mischievous grin was the only warning Shiro got before Keith was blowing the bubbles off of his hands and at Shiro, who in return rolled up the towel in his hands and whipped it at Keith, just barely grazing his right thigh. 

Keith laughed and took the plug out of the sink before rinsing his hands. He was suddenly pulled into turning around by his chin and Shiro’s lips crashed against his. They moved against each other lovingly, mouths opening and tongues entwining. Keith was getting better at it.

When they pulled apart, Keith was panting heavily. Shiro was short for breath, but the change in his breathing was barely noticable. A grin spread across his face. “How about we watch something together, baby brother?”

“I’m not a baby,” Keith whined but was already walking towards the couch and turning the TV on with the remote. “What do you want to watch?”

“Well, I’m up for anything. Is it a smart TV? We could get on Youtube or Netflix.”

Keith knew what he wanted to watch. He brought Youtube up on the screen while Shiro took a seat next to him. The word UNSOLVED came up on the screen in big letters.

“Is this.. Buzzfeed Unsolved?”

“This episode is about aliens! UFOs! Shiro, we live in such a huge universe, we can’t be the only world with life!”

Shiro laughed and kissed his cheek, settling in to watch the show. Keith was watching intently, but Shiro doubted this was the first time he watched it. Funny kid.

After almost thirty minutes, the episode was over, and the autoplay led them into the rabbit hole of conspiracy and horror story videos. By the time their parents returned Shiro was holding his little brother in his arms and the TV was off, Keith too scared to keep watching. All of the lights in the house were on per Keith’s request.

They all ate dinner together, Keith shaking the entire time. When everyone went to their individual rooms, Keith was quick to move into Shiro’s room and climb into his bed.

Shiro rubbed his little brother’s back to soothe him. “Hey.. what if I make you feel nice? Will that help?” A blush spread over Keith’s cheeks, but he nodded. Shiro tugged Keith’s pajama pants down slowly, fingers rubbing circled over Keith’s hips to help calm him before one hand wrapped around his cock.

Shiro stroked slowly, scooting further down the bed and propping himself up on his elbows so that he could take the littler penis into his mouth. His tongue swirled around the head and teased the slit before he took it all of the way into his mouth and sucked around it. Hands tangled in his hair as he bobbed his head.

Keith pulled on the hair, gasping softly, letting out a quiet whimper when Shiro pulled off. “Gotta keep quiet, Keith.. Mom and Dad can’t know about this. Bite the pillow if you have to, okay?” Keith nodded quickly.

Returning to suckling the cock, Shiro’s hand stroked his own erection in time. Keith’s teeth dug into the pillow as he muffled his moans in it, coming clear liquid down Shiro’s throat. Shiro released his come into his own palm and wiped it off on his shirt before taking it off and tossing it onto the floor.

He held Keith’s close and nuzzled his neck. “Sleep well..”

And Keith did.


	5. Chapter 5

**Summary for the Chapter:**

> I just found on my desktop that I had actually written a cute fluffy chapter 5 and not posted it, so we're going to hold off on the Shiro being found out thing and I'm going to post this now. Oops.

Shiro woke up in a tangle of limbs with his brother, who had pulled his pajama pants up sometime during the night. He could hear creaking of the floorboards outside of his room and a bit of light shown through the barely-open door. His mom's soft voice whispered, "Our boys are so cute.."

He could hear his father chuckle and then the door closed and he held Keith closer. Good thing they hadn't fallen asleep nude. With a kiss on Keith's forehead, he sat up carefully, trying not to wake the younger boy. He was soon up and out of the blankets and he went to use the restroom and brush his teeth before meeting his parents downstairs in the kitchen. They would be home for the next week at least, with Christmas so close. He knew they made sure to get as much time off for the holiday as they could. 

"You're up early, darling!" His mom smiled. "Did you sleep okay?"

"Yeah, had to comfort Keith though. He got freaked out last night and ended up sleeping in my room." Telling his parents before one of them mentioned it was the smart move—it would make it seem like he had nothing to hide about Keith being in there. Not that their parents would guess what they were doing, but this lowered those chances. "Do you want me to go wake him up for breakfast?"

"In a bit, maybe. I just got started so breakfast will be a little while, and we might as well let him sleep in."

Shiro nodded and flopped onto the couch. Maybe he could take Keith to the mall or to see a movie, have a fun day out of the house. It'd be nice for both of them to get out of the house, and their parents could have a day off without their kids bothering them, so it would be a win all around. Especially if he could kiss Keith again. Just one more time, really.

Keith appeared at the bottom of the stairs, completely silent on his way down. He rubbed his eyes and sat down by his older brother. He glanced at their parents over the back of the couch, making sure they couldn't see as his hand slipped inside of Shiro's pajama pants. Shiro did well at his maintaining his calm manner, managing to keep up conversation with their parents while Keith's hand wrapped around his rapidly hardening cock. When their mom started bringing out plates of food and Keith had to pull his hand back, Shiro was on edge.

Desperately, he glanced over at Keith, whose hand retreated back so as not to be discovered. Shiro kept himself calm as they ate breakfast, cock aching before eventually limping again. "I was thinking I could take Keith out today? If I can borrow the car..?"

Their parents glanced at each other, as though speaking telepathically, before their mom nodded. "Alright, where will you boys go?"

"Wherever Keith wants.. Maybe the mall?" Shiro shrugged.

Their mother gave him money despite his refusing it, and soon the two were in the car and on their way.

"So, little dude, where do you want to go?"

"First of all, I'm not little, you're just huge. Second of all.. You said the mall before?"

"Yeah, but we can go wherever you want. How about the mall and then we can go see a movie?"

A smile spread across Keith's face and he nodded. "I'd like that." Keith's hands twisted the strap of the polaroid camera he wore around his neck, a gift Shiro gave him last year. "Could we get some pictures together? For my wall.."

How could Shiro say no? when they parked the car they leaned in together over the armrest between them and Keith snapped the picture. He the developing photo and waited to see the image of them, smiling. Shiro took the camera and held it up again. "One for my wall, too."

As he snapped the picture, he pressed his lips to Keith's and smiled as Keith happily pressed back. Maybe the photo wouldn't go on his wall.. But he would keep it for sure.

Keith pulled back, blushing, and sheepishly smiled up at him. "S-so, where to first?"

**Author's Note:**

> Not making promises, but most likely longer and more detailed chapters in the future!


End file.
